<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js返回值</title>
</head>
<body>

<script>
  
    function getFilename(z) {
        var str = new Array();
        str = z.split('.');
        return (str[str.length-1]);
    }
       console.log (getFilename('x564f.hytfx.html.jpg'));

</script>
</body>
</html>